The present invention relates to an alarm system for detecting a dangerous or abnormal condition such as gas leakage and giving a warning signal.
A wide variety of the alarm systems of the type described have been devised and demonstrated, but all of them utilize DC amplifiers, so that a relatively long time is required for the offset adjustment in the production line. Furthermore, the misadjustments result in the erroneous operation of the alarm systems; that is, the variations in the contents level at which the alarm systems must be actuated. As a result, the alarm system fails to operate even when the contents of gas rises above a dangerous level. Moreover, the variable resistors used for the offset adjustments exhibit unsatisfactory aging characteristics, resistance to shock and gas and so on. One solution to this problem is the use of totally enclosed variable resistors, but the cost inevitably increases.